The processing of semiconductor wafers to form integrated circuits often requires a precise control of temperature. As device dimensions are reduced the control of the wafer temperature during processing is becoming a more critical component in maintaining high integrated circuit manufacturing yields. In particular with the increased use of ultra-low K (ULK) dielectrics, wafer-degas processing and temperature control are becoming more critical. Rapid and reliable wafer temperature measurement is currently not available in lamp-heated degas chambers.
A number of methods are currently being used to obtain the semiconductor wafer temperature during processing. Thermocouples built-in to the tools are often used but are usually not in direct contact with the wafer. This can lead to temperature differences of as much as 50° C. during temperature transients. In addition, the built-in thermocouple is often affected by emissivity variation in the system. Dummy wafers with thermocouples built-in to the wafer are used but are very cumbersome and not suitable for in-situ temperature measurements during single wafer processing. Temperatures measurements made using wafers carrying CMOS-based temperature-sensor arrays are limited to temperatures less than 150° C. by the battery, the battery life, and the circuitry required for such measurements.
Current single wafer manufacturing tools pose special problems in obtaining accurate and reproducible temperature measurements. The pyrometers used in a vast majority of such systems are affected by emissivity variations that introduce inaccuracies in the temperature measurement.
There is therefore a need for a rapid reliable wafer temperature measurement apparatus and method. The instant invention addresses this need.